The American black bear (Ursus americanus) has been called a metabolic marvel 6 . In northern Minnesota, where we have conducted long-term physiological and ecological studies of this species, bears may remain in their winter dens for 6 months or more without eating, drinking, urinating or defecating and yet lose very little muscle mass 2 . We also found that hibernating black bears elicit asystolic events of over 30 seconds and experience an exaggerated respiratory sinus arrhythmia 2 . In this previous work we employed Medtronic Reveal ® XT devices that required us to visit the den and temporarily extract the bear (under anesthesia) to download the stored data. 4 Here we describe Medtronic's latest generation of Insertable Cardiac Monitor (ICM), the Reveal LINQ TM , which enables continuous transmission of data via a relay station from the den site 3 . Black bear hibernation physiology remains of high interest because of the multiple potential applications to human medicine.ICMs have been used for nearly two decades by clinicians as a critical diagnostic tool to assess the nature of cardiac arrhythmias in humans. Such devices are primarily implanted subcutaneously to record electrocardiograms. The device size, battery life and transmission capabilities have evolved in recent years. The first devices were relatively large and a programmer was needed to retrieve information during each clinical (or in our case, den visit). These devices were programmed to capture cardiac incidents such as asystolic events, arrhythmias and tachycardias and apply algorithms that ensure proper data collection: e.g. ectopy rejection and p-wave presence algorithms.The new generation Reveal LINQ was made to telemetrically transmit heart data from human patients, but we needed to develop a system to enable transmission from bear dens, which are remote (cannot easily be checked and adjusted) and are subject to extreme winter weather conditions. Besides the advantage of these devices transmitting data automatically, they are considerably smaller and thus less prone to rejection by the extraordinary immune system of the hibernating bear 1 . MethodsFor the past three years, we implanted Medtronic Reveal ® LINQ devices into a study group of black bears (n=18), typically in mid-December, about 2 months after they entered dens. We revisited these bears in early March, about a month before they left dens, to check their body condition and status of the ICM. Denning bears were anesthetized with an intramuscular injection of Telazol ® , and temporarily removed from the den. A small incision was made in a left peristernal location, and the device injected subcutaneously using the insertion tool packaged with the ICM. The optimal positioning was verified by ensuring that the R-wave amplitudes were at least twice the T-wave amplitudes.Remote relay stations were setup at each bear's den (Figure 1). An antenna was placed beneath the bear's natural bedding material (typically leaves or grass) within the den and this cable fed out to a weather-proof box...
Virtual reality (VR) is becoming more widely available and accessible as a technology due to the affordability of cheap computing power. Thus, it has made it possible for virtual reality systems to capture audiences in industry and education, as well as for personal use. Currently, a major limitation of VR headsets is that the user’s vision is completely occluded, making it difficult for them to interact with others. This is problematic in an educational setting since it is difficult for the given instructor and students to have a shared learning experience. Here, we have developed anaglyph 3D functionalities into the Visible Heart® Laboratories anatomical virtual reality platform. These functionalities augment what is viewed by the virtual reality user with an anaglyph shader which in turn projects it to an external display. This allows a multitude of users to wear anaglyph “red/blue 3D glasses” and view the same anatomy as the VR instructor is viewing in 3D, but while preserving the important 3D anatomical spatial relationships.
Cardiac transplant outcomes can be compromised by the effects of global ischemia and associated reperfusion injury. In attempts to alleviate these phenomena, various pharmaceutical agents can be administered. Previous reports have shown that adenosine triphosphate (ATP) may act as either a postconditioning (PoC) or supplementary (Sup) therapy with cardiosupportive benefits. To further evaluate ATP’s relative effectiveness, we used an isolated swine heart four-chamber working model to monitor both hemodynamic and metabolic responses. We employed two strategies of ATP administration: (1) a postconditional (PoC) bolus just prior to reanimation, and (2) regular dosing throughout the assessment period (Sup). Ex vivo swine hearts in the Sup group elicited significantly higher left ventricular function during the 2 h monitoring period than controls. In contrast, PoC administration appeared to induce depressed cardiac function. The effects of ATP on cardiac function can have varied effects, dependent on when it is administered. Impact statement We employed an isolated swine heart four-chamber working model to investigate two potential strategies for adenosine triphosphate (ATP) administration as an ex vivo therapy: (1) application of a single bolus dose during reperfusion (postconditioning or PoC), and (2) repeated bolus dosing throughout the experiment (supplementary or Sup). Ex vivo swine hearts in the Sup group elicited significantly higher left ventricular function during the 2 h experimental monitoring period. In contrast, ATP administration in the PoC group appeared to induce a degree of depressed hemodynamic function. These data suggest varied functional roles of ATP administration relative to their use in ex vivo perfusion strategies. We consider that both treatment strategies, if appropriately administered and with further investigation of dosing paradigms, may eventually elicit value in various clinical scenarios, including heart transplantation and ex vivo heart perfusion to assess potential organs for transplantation and potentially increase the pool of viable donor hearts.
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